From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: "Kulasek, TomaszX" <tomaszx.kulasek@intel.com>,
"dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] examples/l3fwd: fix segfault with gcc 5.x
Date: Mon, 4 Apr 2016 19:06:28 +0000 [thread overview]
Message-ID: <2601191342CEEE43887BDE71AB97725836B2E246@irsmsx105.ger.corp.intel.com> (raw)
In-Reply-To: <1459781123-7556-1-git-send-email-tomaszx.kulasek@intel.com>
> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Tomasz Kulasek
> Sent: Monday, April 04, 2016 3:45 PM
> To: dev@dpdk.org
> Subject: [dpdk-dev] [PATCH] examples/l3fwd: fix segfault with gcc 5.x
>
> It seems that with gcc >5.x and -O2/-O3 optimization breaks packet grouping
> algorithm.
>
> When last packet pointer "lp" and "pnum->u64" buffer points the same
> memory buffer, high optimization can cause unpredictable results. It seems
> that assignment of precalculated group sizes may interfere with
> initialization of new group size when lp points value inside current group
> and didn't should be changed.
>
> With gcc >5.x and optimization we cannot be sure which assignment will be
> done first, so the group size can be counted incorrectly.
>
> This patch eliminates intersection of assignment of initial group size
> (lp[0] = 1) and precalculated group sizes when gptbl[v].idx < 4.
>
> Fixes: 94c54b4158d5 ("examples/l3fwd: rework exact-match")
>
> Signed-off-by: Tomasz Kulasek <tomaszx.kulasek@intel.com>
> ---
> examples/l3fwd/l3fwd_sse.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/examples/l3fwd/l3fwd_sse.h b/examples/l3fwd/l3fwd_sse.h
> index f9cf50a..1afa1f0 100644
> --- a/examples/l3fwd/l3fwd_sse.h
> +++ b/examples/l3fwd/l3fwd_sse.h
> @@ -283,9 +283,9 @@ port_groupx4(uint16_t pn[FWDSTEP + 1], uint16_t *lp, __m128i dp1, __m128i dp2)
>
> /* if dest port value has changed. */
> if (v != GRPMSK) {
> - lp = pnum->u16 + gptbl[v].idx;
> - lp[0] = 1;
> pnum->u64 = gptbl[v].pnum;
> + pnum->u16[FWDSTEP] = 1;
> + lp = pnum->u16 + gptbl[v].idx;
> }
>
> return lp;
> --
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
> 1.7.9.5
next prev parent reply other threads:[~2016-04-04 19:06 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-04 14:45 Tomasz Kulasek
2016-04-04 15:34 ` Ananyev, Konstantin
2016-04-04 15:51 ` De Lara Guarch, Pablo
2016-04-04 16:20 ` Kulasek, TomaszX
2016-04-04 19:05 ` Ananyev, Konstantin
2016-04-05 12:02 ` Kulasek, TomaszX
2016-04-04 19:06 ` Ananyev, Konstantin [this message]
2016-04-06 9:27 ` Thomas Monjalon
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